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Isaque Saes Lanfredi and Ricardo de Camargo

1. Introduction Cold-air incursions across South America can present particular characteristics due to the presence of the Andes Mountains, which contribute to the advancement of cold fronts to the southwest of the Amazon basin. Besides organizing the convection in northern Brazil ( Garreaud and Wallace 1998 ), the continental fronts are also known to cause impacts that are especially felt by agriculture because of freeze events, with significant losses in coffee production and consequent

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Shawn M. Milrad, Eyad H. Atallah, and John R. Gyakum

-level cyclone center starts to intensify over the ocean. A weak negative anomaly is visible at t = −36 h over the Great Lakes region ( Fig. 12d ) and approaches St. John’s from the south at t = 0 h ( Fig. 12g ). The suggestion here is that baroclinic instability is present, as the near-surface cyclone helps to intensify the upstream upper-level trough by advecting cold air beneath 500 hPa (not shown) into the base of the 500-hPa trough. In examining Figs. 12f–h , the 500-hPa negative height anomaly

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Yeong-Min Cha, Hwa-Woon Lee, and Soon-Hwan Lee

by an orographic effect over the Taebaek Mountains. Kang (2000) and Jung et al. (2005) demonstrated the importance of sensible heat flux in heavy snowfall development using the Colorado State University (CSU) Regional Atmospheric Modeling System (RAMS) and the MM5. During snowfall caused by airmass transformations, cloud streets are often observed around large lakes and the open ocean ( Tripoli 2005 ). These cloud streets develop when cold air masses pass over the relatively warm sea surface

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Jared A. Rackley and John A. Knox

1. Introduction Topography is known to affect synoptic and mesoscale weather patterns throughout the world. One such effect, cold-air damming (CAD), occurs when a shallow, surface-based layer of relatively cold air becomes entrenched against the windward side of a mountain range ( Richwien 1980 ). The shallow dome of cold and stable air that becomes established during a CAD event is often identified by the characteristic “U”- or “wedge”- shaped inverted ridge that appears in the sea level

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Qiaoping Li, Song Yang, Tongwen Wu, and Xiangwen Liu

1. Introduction Cold surges are the most conspicuous weather events during winter in East Asia, especially those associated with intensified Siberian high (SH), and exert a major impact on socioeconomical human activities. During the occurrence of a cold surge, cold air breaks out and moves southward along the edge of the expanded SH, leading to severe weather events such as a large temperature drop, strong wind, and heavy freezing rain or snowfall ( Boyle and Chen 1987 ; Ding 1994 ; Chan and

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Ooi See Hai, Azizan Abu Samah, Sheeba Nettukandy Chenoli, Kumarenthiran Subramaniam, and Muhammad Yunus Ahmad Mazuki

climatological base period for the reanalysis data is chosen as 1981–2010 while that for TRMM is from 1998 to 2013. To detect all of the surge-induced events due to the cold-air outburst from the Siberian high moving toward the equatorial South China Sea, we adopt the cold surge index from Chang et al. (2005) , which is chosen as the averaged 925-hPa meridional wind between 110° and 117.5°E along 15°N ( Fig. 5a , described in more detail below). By adapting the index definition from Chang et al. (2005

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Tsing-Chang Chen, Jenq-Dar Tsay, Jun Matsumoto, and Jordan Alpert

of synoptic systems for SCS TS/TY genesis during May: easterlies originated from the northeast Asian cold-surge-like flow and easterlies fed by the western North Pacific cold-air outbreak. Of the 17 identified geneses for TSs/TYs in the SCS, 12 belong to type 1 cyclonic shear flow and 4 belong to type 2 cyclonic shear flow. The genesis for TY Cecil unusually occurred in an SCS cyclonic shear flow formed by the monsoon westerlies and the wake low of TY Brenda. TS/TY geneses occurred in May in 14

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Andrew A. Taylor and Lance M. Leslie

AVN MOS forecasts are too cold as well. Other AVN MOS forecasts south of the high are too warm, notably in Louisiana and south Texas. Forecasts for BNO on 14 February are still very much above the observed temperatures. Pronounced differences in the errors in the NGM and AVN forecasts develop on 15 February. First, the NGM forecasts are less accurate than the AVN forecasts in the region affected by the secondary surge of arctic air (mostly Montana and Wyoming), although both sets of forecasts are

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James J. Gurka, Eugene P. Auciello, Anthony F. Gigi, Jeff S. Waldstreicher, Kermit K. Keeter, Steven Businger, and Laurence G. Lee

curve (i.e., white= cold, and black = warm). Often, the leading edge of the dry surges were associated with a 500-mb wind speed maximum. Duringand just prior to rapid deepening, the dry surges tendedto move rapidly, increase in area, and become warmer(drier) and better defined. Perhaps one mechanism forthis rapid warming apparent on the moisture channelimagery could be tropopause folding, and an associatedextrusion of stratospheric air into the troposphere asdefined by Reed (1955) and Reed and

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Vivek N. Mahale, Jerald A. Brotzge, and Howard B. Bluestein

). The WSR-88D ( Table 1 ) has several set VCPs for its scanning strategy ( Office of the Federal Coordinator for Meteorological Services and Supporting Research 2013 ). For clear air, VCP 31 and 32 are used to provide enhanced sensitivity to detect low-reflectivity echoes ( Office of the Federal Coordinator for Meteorological Services and Supporting Research 2013 ). These VCPs are useful for detecting the early formation of precipitation and help in identifying airmass boundaries (e.g., cold fronts

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